1. Field of the Invention
This invention relates to the treatment of solutions used in a printing process, and in particular, though not exclusively, to the treatment of dampening or fountain solutions used in lithographic printing.
2. Description of the Related Art
The fountain solution is the liquid which is applied to the printing plate of a lithographic press so as to desensitize the background or non-image areas on the latter, i.e. only those areas that are not to be receptive to ink. It commonly consists of water, to which other substances are usually added for various purposes. In this connection it is conventional to add one or more wetting agents, for example long and short chain alcohols (notably isopropyl alcohol), fatty acid esters, glycol and butanol esters, and a large variety of surfactants. Most of these agents emit volatile organic compounds, which, as has long been recognized in the printing industry, has a major disadvantage, mainly for safety and environmental reasons. Other disadvantages are also well known.
Various ways to reduce or eliminate the use of chemical additives so as to reduce these drawbacks, especially the emission of volatile organic compounds, have been proposed. One of these proposals involves the direct injection of electromagnetic radiation at a radio frequency (typically around 43 KHz) into the solution, via an injector which is coupled to an RF generator by means of a tuned cable.
In this last-mentioned proposal, the injector transmits the RF signals into the fountain solution by means of a conductor which is in direct contact with the liquid to be treated.